9. Nick Fury's Eye Injury - Captain Marvel
The fact that Nick Fury doesn't really have that much of a backstory in the MCU is probably for the best.
Aside from seeing him at different points working with SHIELD, his role as the puppeteer behind the Avengers seems to be the ideal place for him, not really letting any of the minute details of his personal life slip out. Although we did see a bit more of his history with SHIELD in Captain Marvel, it's nice that we at least know where the eyepatch came from.
Towards the end of Captain Marvel, we find out that the alien cat Goose has been the culprit behind Fury's eye injury, having scratched it out while they were helping the Skrulls to safety. As much as this could have been just a funny aside, it gets that much better once you've watched the rest of the MCU movies.
When going back to something like Captain America: The Winter Soldier now, the idea of Fury telling Cap that he lost an eye the last time he trusted someone feels all the more hilarious when you realize who's behind everything. Then again, if you have a face as precious as Goose's, you would probably give an eye for that kind of feline too.